1. Field of the Invention
The present invention relates to an inerting method for reducing the risk of an outbreak of fire in an enclosed space as well as a device for realizing the method.
2. Description of the Related Art
Known as a measure to counteract the risk of fire in enclosed spaces in which people only enter occasionally, for example, and in which the equipment therein reacts sensitively to the effects of water, is lowering the oxygen concentration in the respective area to a value of, e.g., about 12% by volume. Most inflammable materials can no longer burn at this oxygen concentration. The main area of application of the present invention hereto are IT areas, electrical switchgear and distributor compartments, enclosed facilities as well as storage areas for high-value commodities.
For example, the specification of German patent application DE 198 11 851 C1 describes an inerting device for reducing the risk of, and extinguishing fires in, enclosed spaces. The known system is thereby designed to reduce the oxygen content in an enclosed space to a predefinable base inertization level and in the event of a fire or when otherwise required, to quickly reduce the oxygen content further to a defined full inertization level so as to enable effective extinguishing of a fire while keeping the storage requirements for inert gas cylinders to a minimum. To this end, the known device includes an inert gas system controllable by a control unit, as well as a supply pipe system connected to the inert gas system and the protected space through which the inert gas provided by the inert gas system is fed into the protected space. Conceivably, the inert gas system would either be a pressure cylinder battery which stores the inert gas in compressed form, a system to produce inert gases, or a combination of both solutions.
The type of system described at the outset concerns a method, and respectively a device, to reduce the risk of, and extinguish fires as needed, in the monitored protected space, whereby continuous inerting of the protected space is likewise used for the purpose of preventing or controlling fires. As stated above, inerting methods function based on the knowledge that under normal conditions, the risk of fire can be countered in enclosed spaces by lowering the oxygen concentration in the respective area to a constant value of, for example, 12% by volume.
The resulting preventative and extinguishing effect of the inerting method is hereby based on the principle of oxygen displacement. As is generally known, normal ambient air consists of 21% oxygen by volume, 78% nitrogen by volume and 1% by volume of other gases. To effectively lower the risk of a fire breaking out in a protected area, the oxygen concentration in the area at issue is reduced by introducing inert gas or an inert gas mixture such as, e.g., nitrogen. An extinguishing effect is known to occur in the case of most solids when the percentage of oxygen falls below about 15% by volume. Depending on the inflammable materials contained within the protected area, further lowering of the oxygen percentage to, e.g., 12% by volume may be necessary. In other words, this means that by subjecting the protected space to continuous inertization at a so-called “base inertization level” in which the oxygen percentage in the ambient air is reduced to below 15% by volume, the risk of a fire developing in the protected area can also be effectively reduced.
The term “base inertization level” as used herein is to be generally understood as a reduced oxygen content with regard to the ambient atmosphere of the protected space in comparison to the oxygen content of the normal ambient air, whereby from a medical standpoint, however, this reduced oxygen content does not in principle pose any risk whatsoever to persons or animals, so that they—possibly taking certain precautionary measures—can still enter into the protected space.
As indicated above, setting a base inertization level which, in contrast to the so-called “full inertization level,” does not necessarily correspond to a reduced oxygen percentage at which effective extinguishing occurs, primarily serves to reduce the risk of a fire from breaking out in the protected space. The base inertization level corresponds to an oxygen content—depending on the circumstances of the individual case—of for example, 13% to 15% by volume.
Conversely, the term “full inertization level” refers to an oxygen content which has been reduced further compared to the oxygen content of the base inertization level and at which the inflammability of most materials is already lowered to the point of no longer being ignitable. Depending on the fire load within the protected space at issue, the oxygen concentration at the full inertization level is normally 11% to 12% by volume.
The solutions known to date which use an inerting method to extinguish fires or to minimize the risk of a fire breaking out in enclosed spaces are designed such that all the goods stored in the enclosed space are incorporated into the fire prevention concept. It is, however, often not necessary to subject the entire volume of the enclosed space to continuous inertization as a preventative measure, since only certain areas of the space may serve to store inflammable materials, for example, while other areas of the space remain unused or store non-combustible materials. Particularly in large warehouses, a continuous inertization of the entire stockroom volume would only make economic sense when the entire volume of the space is actually used to store combustible materials.
Since particularly the consumer goods and foodstuff industries are intimately geared to consumer behavior and changes in consumer behavior have a direct impact on the market, it is desirable for the retail market to be able to react as flexibly as possible to any restructuring of storage or transportation conditions. Warehouses able to particularly easily adapt their storage capacity and storage conditions to the respective market situation are therefore in demand. The same holds equally true for inerting systems frequently used in such warehouses as preventative protection against fire.